I would expect light rain in pittsburgh over the next 24 to 48 hours. The lower/falling pressures in cities to the west indicate that a low pressure system is moving from west to east toward pittsburgh. Low pressure systems are normally associated with precipitation. The fact that you do not see a big drop in temperature in the more western cities indicates the low pressure system is moving with a warm front, so only light rain would be expected. Heavy rains or more violent weather is only normally associated with cold fronts, where the warm air is pushed up and over a cold front rapidly. This rapidly rising air (convection) is what gives you heavier torrential rains, and other potentially severe weather conditions.
